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Biology LibreTexts

13. 32: Respiration

Where does oxygen get into blood?

Red blood cells are like trucks that transport cargo on a highway system. Their cargo is oxygen, and the highways are blood vessels. Where do red blood cells pick up their cargo of oxygen? The answer is the lungs. The lungs are organs of the respiratory system. The respiratory system is the body system that brings air containing oxygen into the body and releases carbon dioxide into the atmosphere.


The job of the respiratory system is the exchange of gases between the body and the outside air. This process, called respiration, actually consists of two parts. In the first part, oxygen in the air is drawn into the body and carbon dioxide is released from the body through the respiratory tract. In the second part, the circulatory system delivers the oxygen to body cells and picks up carbon dioxide from the cells in return. The lungs are organs of the respiratory system. It is in the lungs where oxygen is transferred from the respiratory system to the circulatory system.

The use of the word “respiration” in relation to gas exchange is different from its use in the term cellular respiration. Recall that cellular respiration is the metabolic process by which cells obtain energy by “burning” glucose. Cellular respiration uses oxygen and releases carbon dioxide. Respiration by the respiratory system supplies the oxygen and takes away the carbon dioxide.

  • Respiration is the process in which gases are exchanged between the body and the outside air.
  • The lungs and other organs of the respiratory system bring oxygen into the body and release carbon dioxide into the atmosphere.


  1. What is respiration?
  2. Describe the two parts of respiration.
  3. How is respiration different from cellular respiration?